Piezo-electrically induced hydraulic movement of a magnetron tuning element

ABSTRACT

The tuning member of a magnetron is moved hydraulically by liquid which is moved by a piezo-electric element. The piezoelectric element forms part of a chamber containing the liquid, the tuning member being moved by the movement of the liquid in a conduit, of relatively small bore, in communication with the chamber. There may be two chambers and two conduits, providing a push-pull arrangement for moving the tuning member.

I United States Patent 1 [111 3,761,764

Brady Sept. 25, 1973 [54] PIEZO-ELECTRICALLY INDUCED 3,478,246 11/1969Perkins et a1. 315/3961 X HYDRAULIC MOVEMENT OF A 3,671,801 6/1972Masek.... 315/3961 3,478,247 11/1969 Hull .1 315/3961 X MAGNETRON TUNINGELEMENT 3,187,220 6/1965 Dench.... 315/3961 X [75] Inventor; MichaelBarry Brady, Maldon, 2,589,885 3/1952 Sonkin 315/3959 England [73]Assignee: English Electric Valve Company Primary ExaminerRudolph V.Rolinec Limited, Chelmsford, England Assistant ExaminerSaxfield Chatmon,Jr. [22] Filed: Feb 18, 1972 Atl0rneyDonald M. Wight et al.

[21] Appl. No.: 227,366

[57] ABSTRACT 30 F A l' t' 't orelgn pp y Data The tuning member of amagnetron is moved hydrauli- Mar. 17, Great Bi'llall'l uy is moved apiezo electric ment. The piezo-electric element forms part of a cham-[22] Cl 315/3961, BIS/39.55, 315739.77 Containing the liquid; the tuningmember being .1; movcd the movement Of the in a conduit of 1 held 0Search 5/39" relatively small bore, in communication with the cham-39'57 ber. There may be two chambers and two conduits, rovidin a ushullarran ement for movin the tun- [56] References Cited p g g UNITED STATESPATENTS 3,262,009 7/1966 Sibley 315/396] 7 Claims, 6 Drawing FiguresPATENTEDSEP25|975 3761.764

SHEET 10F 3 PATENTEDSEPZSlHH SHEET 2 [IF 3 nae PATENTEUSEMSM 3,761,764

SHEET 3 BF 3 PIEZO-ELECTRICALLY INDUCED HYDRAULIC MOVEMENT OF AMAGNETRON TUNING ELEMENT This invention relates to magnetrons and morespecifically to magnetrons of the kind in which there is provided atleast one member, which in some cases is metallic and in others is ofdielectric material, and means for moving the same in relation to theanode block of the magnetron to vary the frequency generated thereby.There are many known varieties of magnetron of this kind and movingmember or members of various forms have been proposed for example amoving member in the form of a metal ring carried adjacent one end ofthe anode block of a so-called rising sun" magnetron and movable towardsand away from the block or one or more moving members in the form of oneor more metal or dielectric slugs inserted in and movable to and froendwise with respect to one or more of the holes in the anode block of aso-called hole and slot magnetron.

Considerable difficulties are experienced in designing satisfactorymagnetrons of the kind referred to and the practical requirements are byno means easy to satisfy together. These requirements include providingan adequate range of variation of frequency for tuning or frequencymodulation purposes and this involves providing an adequate range ofmovement of the tuning member or members; avoiding disturbing effectsdue to mechanical resonances in the mechanically moving system whichincludes the moving member or members and the driving means thereforsuch avoidance is particularly difficult to achieve if the movement ofthe driving means is much smaller than the required movement of themoving member or members; securing a sufficiently rapid response of themoving member or members and therefore a sufficiently rapid change isgenerated frequency when a control force is applied to move the drivingmeans for said member or members; and making the whole mechanicallymoving system such as to avoid the need for expensive and mechanicallyunsatisfactory or inefficient expedients, such as magnetic driving linksand making parts of the evacuated envelope of the magnetron of flexibleconstruction (as has been proposed) in order to transmit mechanicaldrive from driving means outside the said envelope to a moving member ormembers inside it. Also a wide variety of electro-mechanical transducershas been proposed in order .to translate a control voltage intomechanical movement of a driving device. Such transducers includeelectro-magnetic transducers such as solenoids and piezo-electrictransducers. Piezo-electric transducers have the advantages of highefficiency, low losses, and an ability to provide powerful mechanicaldriving forces. They have however the important defect that themechanical movement obtainable therefrom is of small amplitude. If, inorder to overcome this, a mechanical drive of large mechanical advantageis used to obtain, from a piezo-electric driving transducer, mechanicalmovement of adequate extent from a driving member or members driventhereby, the already mentioned difficulties of disturbance by resonanteffects and limitation of rapidity of response arise. Moreover themounting of a piezo-electric transducer inside the evacuated envelope ofa magnetron has the disadvantage that its operation may become impairedby the sputtering of metal on the crystal between its electrodes and/orby the effects of heating, for the Curie point of currently availablepiezo-electric crystals is relatively low, being only about 300 C. Ifthe crystal is mounted outside the evacuated envelope there is theproblem of providing a satisfactory mechanical drive through saidenvelope.

The present invention seeks to provide a solution of the foregoingdifficulties.

According to this invention in its broadest aspect a magnetron of thekind referred to comprises at least one liquid-filled chamber,piezo-electric means for varying the volume of said chamber, liquidfilled conduit means in communication with the liquid in said chamberand a moving member or members adapted, upon movement thereof to varythe frequency of said magnetron, and hydraulically driven through saidconduit, the whole arrangement being dimensioned to provide, in responseto a given movement of said piezoelectric means, a movement of saidmember or members magnified by mechanical advantage obtainedhydraulically.

Preferably there are two chambers, two piezoelectric means, one for eachchamber, and two conduits of relatively small bore, one leading fromeach chamber to hydraulic means for driving the moving member ormembers; and the piezo-electric means are arranged to be activated inphase opposition so that the said member or members are driven in onedirection through one conduit and in the other through the other.

Preferably the chamber or each chamber, has part of its wall constitutedby a body of piezo-electric crystal so that the chamber andpiezo-electric means are unitary with one another to constitute achamber, the volume of which will be varied by mechanical movements ofthe crystal body.

Preferably again each chamber consists of a cylindrical piezo-electricmember and means are provided for simultaneously applying equal andopposite drive signals, one to each cylinder, whereby one axiallycontracts whilst the other axially expands.

Preferably the hydraulic means for driving the moving member or membersis constituted by a further small bore conduit connected between the twoconduits and arranged to extend inside the evacuated envelope of themagnetron through a tuning cavity therein.

In this case the tuning member could be a dielectric or metal slughoused in the further small bore conduit.

For maximum tuning effect it is preferable to have one tuning member foreach cavity. However, where the magnetron is of the external cavity typeit is sufficient to have one tuning member for that cavity.

The invention is illustrated in and further described by way of examplewith reference to the accompanying drawings in which FIG. 1 is adiagrammatic part sectional view of one embodiment of the invention.FIG. 2 is a diagrammatic part sectional view of modification of theembodiment shown in FIG. 1. FIG. 3 is a diagrammatic sectional view of apreferred embodiment of the invention. FIG. 4 is a perspective sketch ofan anode block broken away to better illustrate a detailed portion ofthe present invention and its operation. FIG. 5 is a sectional viewshowing a system as used with the preferred embodiment of the invention;and FIG. 6 is a view illustrating a conventional coaxial magnetron towhich the invention is applied. The remaining parts of the magnetron arestandard and have not therefore been illustrated. Like references denotelike parts in the drawings.

Referring to FIG. 1 this shows a fluid chamber I having a cylindricalbody portion 2 of piezo-electric material and end seals 3 and 4. Endseal 4 has'a central aperture in which is mounted one end of a smallbore conduit 5. The other end of the conduit 5 is connected to asimilarly apertured end seal 6 of a flexible bellows 7 which has anotherend seal 8 to which is connected a tuning element 9.

- In operation drive signals are applied (by means not shown) to thepiezo-electric cylinder 2 to cause the cylinder 2 to axially expand andcontract, thus effectively expanding and contracting the volume enclosedby the chamber 1. This forces fluid from the chamber 1 along conduit 5and moves the tuning element 9 via the flexible bellows 7.

Referring now to FIG. 2 this shows two fluid chambers 10 and 11connected via two conduits 12 and 13 to opposite ends 14 and 15respectively of a double flexible bellows 16. The bellows 16 includes anapertured plate 17 which is fixedly mounted on a rod 18. The rod 18 hasits ends mounted one in conduit 12 and the other in conduit 13 and is asliding fit therein. The apertured plate 17 has a lug 19 extendingexternally of the bellows 16 which carries a tuning element 20.

In operation fluid is forced from either chamber 10 or 11 (they operatein phase opposition, i.e., as one expands the other contracts) alongconduits 12 or 13 respectively to move rod 18. Since this is rigidlyconnected to plate 16 this causes the plate to move axially (asindicated by the double-headed arrow) which in turn moves the tuningelement.

Referring now to FIG. 3 this shows two fluid chambers 21, 22, havingpiezo-electric cylinders 23, 24 respectively, joined back to back with acommon wall 25. The chambers 21, 22 have end walls 26, 27 respectivelysealed into which are small bore metal conduits 28 and 29 respectively.These conduits 28, 29 are joined at their free ends to a further smallbore conduit 30 of ceramic in which is housed a metal tuning slug 3].The piezoelectric cylinders 23, 24 are each coated with inner and outerlayers of metal M to which drive signals may be applied from a signalsource S via leads L. The leads are connected so that equal and oppositesignals are applied to the cylinders. Whilst described as being of metalthe slug 31 could be made of dielectric.

In operation when suitable drive signals are applied from source S topiezo-electric cylinders 23, 24, one chamber, say chamber 21 will expandand the other chamber 22 will simultaneously contract, forcing fluidfrom chamber 22 along conduit 29 via conduit 30 to conduit 28 and thusinto chamber 21. This movement of fluid will move the metal slug 31toward conduit 28.

Similarly, if the drive signal is reversed and chamber 21 axiallycontracts whilst chamber 22 axially expands, fluid will be forced in thereverse direction carrying the slug 31 with it.

Referring now to FIG. 4 this shows an anode block 32 of the so called"hole and slot" type which has been partly broken away to leave fiveholes H. FIG. 5 illustrates part of the system as described above inconjunction with FIGS. 3 and 4.

This drawing shows how the arrangement of FIG. 3 can be applied to aconventional magnetron. In this case the conduits 28, 29, extend outsidethe magnetron envelope (not shown) and conduit 30 ex-tends iide theenvelope through hole H. It can be seen that the slug 31 can thus becontrolled to move up and down in the hole H, the extent of move-mentbeing indicated by the double headed arrow. This enables tuning to beeffected in a simple manner with the piezo-electric crystal members 23,24 outside of the magnetron envelope.

In FIG. 6, a conventional coaxial magnetron is shown and in which thereis included the cathode 33, inner anode 34 and outer anode 35 to presentthe usual external cavity 36. For such an arrangement, a single tuningelement operated as described above is employed as shown. Thus, thesmall bore conduit 30' contains the tuning element 31 operated asdescribed above in conjunction with FIGS. 3-5.

I claim:

1. In a magnetron having at least one tuning element, at least onehollow body defining a liquid-filled chamber, piezo-electric meansforming a portion of said body for varying the volume of said chamber,and hydraulic means communicating with the interior of said chamber formoving said tuning element in response to variations in the volume ofsaid chamber, said hydraulic means defining a second chamber actingagainst said tuning element in which said second chamber is of a volumesubstantially less than the volume of the chamber first mentioned,whereby a given movement of said piezo-electric means effects a movementof said tuning element which is magnified by mechanical advantage gainedhydraulically.

2. In a magnetron as defined in claim 1 including a second hollow bodydefining a third chamber, second piezo-electric means forming a portionof said second body for varying the volume of said third chamber, secondhydraulic means communicating with the interior of said third chamberfor moving said tuning element in response to variations in volume ofsaid third chamber, said second hydraulic means defining a fourthchamber acting against said tuning element in opposition to thehydraulic means first mentioned and in which the volume of said fourthchamber is substantially less than the volume of said third chamber, andmeans for energizing said piezo-electric means first mentioned and saidsecond piezo-electric means in phase opposition.

3. In a magnetron as defined in claim 2 wherein each piezo-electricmeans is in the form of a cylindrical body provided for the externalcavity thereof.

t ll 4' i t

1. In a magnetron having at least one tuning element, at least onehollow body defining a liquid-filled chamber, piezo-electric meansforming a portion of said body for varying the volume of said chamber,and hydraulic means communicating with the interior of said chamber formoving said tuning element in response to variations in the volume ofsaid chamber, said hydraulic means defining a second chamber actingagainst said tuning element in which said second chamber is of a volumesubstantially less than the volume of the chamber first mentioned,whereby a given movement of said piezo-electric means effects a movementof said tuning element which is magnified by mechanical advantage gainedhydraulically.
 2. In a magnetron as defined in claim 1 including asecond hollow body defining a third chamber, second piezo-electric meansforming a portion of said second body for varying the volume of saidthird chamber, second hydraulic means communicating with the interior ofsaid third chamber for moving said tuning element in response tovariations in volume of said third chamber, said second hydraulic meansdefining a fourth chamber acting against said tuning element inopposition to the hydraulic means first mentioned and in which thevolume of said fourth chamber is substantially less than the volume ofsaid third chamber, and means for energizing said piezo-electric meansfirst mentioned and said second piezo-electric means in phaseopposition.
 3. In a magnetron as defined in claim 2 wherein eachpiezo-electric means is in the form of a cylindrical body portion.
 4. Ina magnetron as defined in claim 2 wherein said first and secondhydraulic means are integrally formed as a small bore conduit and saidtuning element is fitted slidably therein.
 5. In a magnetron as definedin claim 4 wherein said tuning element is a dielectric or metal slug. 6.A magnetron as claimed in claim 1 and wherein there is one tuning memberfor each cavity.
 7. A magnetron as claimed in claim 1 and of theexternal cavity type and wherein one tuning member is provided for theexternal cavity thereof.